package 蓝桥真题;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class 灌溉 {
       static BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
       final static int N=110;
       static int g[][]=new int[N][N],dix[]={-1,1,0,0},diy[]={0,0,-1,1},n,m,k;
       static boolean st[][]=new boolean[N][N];
       static Pair[]p=new Pair[20];
       static void dfs(int x,int y,int d){
    	      if(d>k)return;
    	      st[x][y]=true;
    	      for(int i=0;i<4;i++){
    	    	  int a=x+dix[i],b=y+diy[i];
    	    	  if(a>=1&&a<=n&&b>=1&&b<=m)
    	    		  dfs(a,b,d+1);
    	      }
       }
       static class Pair{
    	      int x,y;
    	      Pair(int x,int y){
    	    	  this.x=x;
    	    	  this.y=y;
    	      }
       }
       public static void main(String[] ss) throws IOException {
		      ss=br.readLine().split(" ");
		      n=Integer.parseInt(ss[0]);m=Integer.parseInt(ss[1]);
		      int t=Integer.parseInt(br.readLine());
		      int res=0;
		      for(int i=0;i<t;i++){
		    	    ss=br.readLine().split(" ");
		    	    int x=Integer.parseInt(ss[0]),y=Integer.parseInt(ss[1]);
		    	    p[i]=new Pair(x,y);
		      }
		      k=Integer.parseInt(br.readLine());
		      for(int i=0;i<t;i++)
		    	  dfs(p[i].x,p[i].y,0);	  
		      for(int i=1;i<=n;i++)
		    	  for(int j=1;j<=m;j++)
		    		  if(st[i][j])res++;
		      System.out.print(res);
		    			  
		      
	}
}
